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Old 30 October 2018, 17:08   #596
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Join Date: Sep 2016
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Originally Posted by roondar View Post
The lack of scrolling prowess for the Acorn with it's ARM2 (as well as machines using 68030's, 386's etc) has always caused me some wonder. These processors should be plenty fast enough to do the whole thing in software and still easily make a 50/60Hz update rate.

A quick back-of-the-envelope calculation suggests that the ARM2@8MHz should be able to smoothly scroll a 320x256, 256 colour screen using no more than about 50% of the CPU time it has. That still leaves quite a bit of bandwidth/CPU power for softsprites, game/demo logic and the like.

The ARMv2 is plenty fast enough to update every frame.. and the barrel shifter makes pixel level scrolling free. see axis as an example game. Amiga coders want hardware way to do it. They don’t like to use their brain.

EDIT: you can preload the MEMC video DMA register ahead of time so it latches on vsync. That’s free veritical scrolling. IIRC You can even poke the VIDC start window regs to get 2 pixel res horizontal scrolling for free.

Yes.. 2 pixel res scrolling.


Last edited by plasmab; 30 October 2018 at 17:23.
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